Don't evaluate args to LOG(INFO) and LOG(WARNING) in release builds.

base/logging.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_LOGGING_H_
 #define BASE_LOGGING_H_
 
 #include <cassert>
 #include <string>
 #include <cstring>
@@ skipping 220 matching lines @@
 // log file/displayed to the user (if applicable). Anything below this level
 // will be silently ignored. The log level defaults to 0 (everything is logged
 // up to level INFO) if this function is not called.
 // Note that log messages for VLOG(x) are logged at level -x, so setting
 // the min log level to negative values enables verbose logging.
 BASE_EXPORT void SetMinLogLevel(int level);
 
 // Gets the current log level.
 BASE_EXPORT int GetMinLogLevel();
 
+// Used by LOG_IS_ON to lazy-evaluate stream arguments.
+BASE_EXPORT bool ShouldCreateLogMessage(int severity);
+
 // Gets the VLOG default verbosity level.
 BASE_EXPORT int GetVlogVerbosity();
 
 // Gets the current vlog level for the given file (usually taken from
 // __FILE__).
 
 // Note that |N| is the size *with* the null terminator.
 BASE_EXPORT int GetVlogLevelHelper(const char* file_start, size_t N);
 
 template <size_t N>
@@ skipping 82 matching lines @@
   COMPACT_GOOGLE_LOG_EX_ERROR(ClassName , ##__VA_ARGS__)
 #define COMPACT_GOOGLE_LOG_0 COMPACT_GOOGLE_LOG_ERROR
 // Needed for LOG_IS_ON(ERROR).
 const LogSeverity LOG_0 = LOG_ERROR;
 #endif
 
 // As special cases, we can assume that LOG_IS_ON(FATAL) always holds. Also,
 // LOG_IS_ON(DFATAL) always holds in debug mode. In particular, CHECK()s will
 // always fire if they fail.
 #define LOG_IS_ON(severity) \
-  ((::logging::LOG_ ## severity) >= ::logging::GetMinLogLevel())
+  (::logging::ShouldCreateLogMessage(::logging::LOG_##severity))
 
 // We can't do any caching tricks with VLOG_IS_ON() like the
 // google-glog version since it requires GCC extensions.  This means
 // that using the v-logging functions in conjunction with --vmodule
 // may be slow.
 #define VLOG_IS_ON(verboselevel) \
   ((verboselevel) <= ::logging::GetVlogLevel(__FILE__))
 
 // Helper macro which avoids evaluating the arguments to a stream if
 // the condition doesn't hold. Condition is evaluated once and only once.
@@ skipping 608 matching lines @@
 #elif NOTIMPLEMENTED_POLICY == 5
 #define NOTIMPLEMENTED() do {\
   static bool logged_once = false;\
   LOG_IF(ERROR, !logged_once) << NOTIMPLEMENTED_MSG;\
   logged_once = true;\
 } while(0);\
 EAT_STREAM_PARAMETERS
 #endif
 
 #endif  // BASE_LOGGING_H_